The potential applications and recognized advantages of employing electrical energy in surgical procedures continue to increase. In particular, for example, electrosurgical techniques are now being widely employed to provide significant localized surgical advantages in both open and laparoscopic applications, relative to traditional surgical approaches.
Electrosurgical techniques typically entail the use of a hand-held instrument, or pencil, that transfers radio frequency (RF) electrical energy to a tissue site, a source of radio frequency (RF) electrical energy, and an electrical return path device, commonly in the form of a return electrode pad positioned under a patient (i.e., a monopolar system configuration) or a smaller return electrode positionable in bodily contact at or immediately adjacent to the surgical site (i.e., a bipolar system configuration). The waveforms produced by the RF source yield a predetermined electrosurgical effect, namely tissue cutting or coagulation.
During transfer of RF electrical energy to a tissue site the parts of the instrument contacting or near the tissue become hot. Among the problems caused by such heating in proximity to tissue is the formation of a coating consisting of tissue and thermally decomposed tissue products, called eschar, that can adhere to the instrument and interfere with its proper function. Electrosurgical instruments have been proposed that are coated with materials in attempts to provide a surface from which eschar is more easily removed than from bare metal. For example, U.S. Pat. No. 4,785,807 describes a stainless steel blade coated with a form of polytetrafluoroethylene (PTFE), U.S. Pat. No. 5,702,387 describes metal blades coated with polysiloxane (specifically, polydiorganosiloxane) elastomer, and U.S. Pat. No. 6,511,479 describes metal blades coated with polysiloxanes. These coatings, and in particular, polysiloxane, coatings tend to be soft and can be removed from the blades with only modest scraping, e.g., by scraping with a thumbnail. The PTFE and the polysiloxane coatings have been found, with use, to recede from the regions closest to where energy discharge occurs leading to an increase in the amount of metal exposed and to lead to excessive heating of at least parts of the instruments, leading to eschar accumulations and smoke. Therefore, for certain applications, the need exists for more durable coatings for such surgical instruments.
Despite numerous advances in the field, currently-employed electrosurgical techniques often generate substantial smoke at the surgical site. Such smoke occurs as a result of tissue heating and the associated release of hot gases/vapor from the tissue site (e.g., in the form of an upward plume). As will be appreciated, any generation of smoke may impede observation of the surgical site during surgical procedures. Additionally, the generation of smoke results in attendant fouling of the atmosphere in the surgical theater. Clearly, these environmental impacts may adversely detract from the performance of medical personnel. Further, there is growing concern that the smoke may be a medium for the transport of pathogens away from the surgical site, including viruses such as HIV. Such concerns have contributed to the use of face shields and masks by surgical personnel.
To date, implemented approaches to deal with smoke have focused on the use of devices that either evacuate the smoke by sucking the same into a filtering system, or that merely blow the smoke away from the surgical site by a pressurized gas stream. Smoke evacuators typically require the movement of large amounts of air to be effective. As such, evacuators tend to be not only noisy but also space consuming. Approaches for blowing smoke away from the surgical site fail to address many of the above-noted concerns, since smoke is not actually removed from the surgical environment. Moreover, both of the above-noted approaches entail the use of added component, thereby increasing the cost and complexity of electrosurgical systems.
Recently, U.S. Pat. No. 6,287,305 has revealed that electrosurgical accessories, including blades, can substantially reduce smoke production by using a metal that has sufficiently high thermal conductivity and insulating the devices except for an exposed edge region where electrosurgical energy is transferred from the accessory to the tissue. Generally, high temperatures occur at the edge such that insulation materials such as silicone elastomers, fluorinated compounds (e.g., PTFE or PFA), and polyimids cannot be used directly on the metal as an insulator. The '305 patent discloses first applying one or more ceramic materials to coat the metal near the edge and then coating the ceramic with another material, such as a silicone elastomer or a fluorinated compound. These configurations require manufacturing process and materials selection that ensure adhesion of the coating material to the ceramic. While effective, such steps can add cost and complexity.